Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h, w = map(int, input().split())
s = []
for _ in range(h):
    s.append(input())
q = deque([(0, 0)])
INF = 10**5
dist = [[INF]*w for _ in range(h)]
dist[0][0] = 0
dxdy = [(-1,0), (0,-1), (0,1), (1,0)]
while q:
    x, y = q.popleft()
    for dx, dy in dxdy:
        if not(0<=x+dx<w and 0<=y+dy<h):
            continue
        if s[y+dy][x+dx]=='#' or dist[y+dy][x+dx]<INF:
            continue
        dist[y+dy][x+dx] = dist[y][x] + 1
        q.append((x+dx, y+dy))
if dist[h-1][w-1]==INF:
    print(-1)
else:
    white = 0
    for r in s:
        white += r.count('.')
    print(white-dist[h-1][w-1]-1)